The present invention relates to an optical fiber positioning member for fixedly positioning optical fibers by placing the optical fibers in concave grooves engraved in one substrate and by holding the optical fibers by the other substrate and a method of fixedly positioning the optical fibers by using the member, and more particularly to an optical fiber array for connecting the optical fibers with integrated optical parts such as optical waveguide ways, photodiodes, laser diodes and integrated optical elements, and to a ferrule, such as an optical connector and an optical splicer.
Heretofore, where a plurality of optical fibers are connected to integrated optical parts, such as optical waveguide ways, photodiodes, laser diodes and integrated optical elements, and where a singular or a plurality of optical fibers are connected to each other through an optical connector or an optical splicer, in order to reduce optical transmission loss between joining surfaces to a low value as possible, a plurality of the optical fibers linearly arranged have been required to have a very high positioning accuracy such that both a horizontal pitch accuracy and a vertical pitch accuracy have been required to be .+-.0.5 .mu.m or less each. The horizontal pitch accuracy means an average value of dislocated widths between optical fibers arranged horizontally; and the vertical pitch accuracy means an average value of vertically dislocated widths of the optical fibers with respect to a horizontal line as a reference.
Now, as shown in FIG. 8, where an optical waveguide way 30 is connected to a plurality of optical fibers 10, in order to arrange the optical fibers 10 to form a line at the above-mentioned positioning accuracy, there has been used an optical fiber positioning member 11 provided with a plurality of V-shaped grooves 3 on the surface thereof such that the respective optical fibers 10 have been placed on the V-shaped grooves 3 of the above-mentioned optical fiber positioning member 11, and then respective optical fibers 10 have been connected at a high accuracy to branched optical waveguide paths 31 of the optical waveguide way 30.
Also, the above-mentioned optical fiber positioning member 11, as shown in FIG. 6, has eight-core V-shaped grooves 3 engraved with a high accuracy in a joining surface 2a, and comprises a first substrate 2 provided with a concave cutout portion 4 at the rear end thereof and a flat plate-shaped second substrate 5 shorter than the above-mentioned first substrate 2, and there have been both the substrates 2, 5 formed of a plastic or a glass, or a ceramic etc. As a method of fixedly positioning respective optical fibers 10 in a ribon optical fiber 20 by using the optical fiber positioning member 11, there has been a method in which respective optical fibers 10 have been placed in the V-shaped grooves 3 of the first substrate 2, an epoxy-based or acryl-based adhesive 15 having thermoset properties or ultraviolet curing properties has been applied to the upper portion thereof, and then the second substrate 5 has been placed from the upper side thereof, and heat or light has been applied to the adhesive 15 to cure, whereby respective optical fibers 10 have been held between the first substrate 2 and the second substrate 5 so as to be positioned fixedly in the V-shaped grooves 3.
However, there has existed a problem that generally the adhesive 15, when cured, changes greatly in volume.
Therefore, in the above-mentioned optical fiber positioning member 11 in which respective optical fibers 10 are positioned fixedly in the V-shaped grooves 3 by the adhesive 15, as shown in FIG. 7, as the adhesive 15 is cured, the second substrate 5 can be dislocated laterally, and at the same time, the optical fibers 10 can be pulled to be separated from the side wall 3a of the V-shaped grooves 3, whereby respective optical fibers 10 can not be fixedly positioned in the V-shaped grooves 3.
Also,the adhesive 15 has changed largely in volume due to an environmental change, so that the respective optical fibers 10 can not be fixedly positioned with high accuracy in the V-shaped grooves 3 of the first substrate 2.
That is, there has been a problem that the adhesive 15 absorbs water content existing in the atmosphere to cause a change in volume, with the result that the optical fibers 10 are separated from the side wall 3a of the V-shaped grooves 3. Also, even when used at a high temperature, the adhesive 15 changes its volume, whereby the optical fibers 10 could not be fixedly positioned at a high accuracy in the V-shaped grooves 3.